cm:Concept: us-gaap:OtherThanTemporaryImpairmentLossesInvestmentsAvailableforsaleSecuritiesPortionRecognizedInEarningsNetQualitativeDisclosuresSignificantInputs
| Other than Temporary Impairment Losses, Investments, Available-for-sale Securities, Portion Recognized in Earnings, Net, Qualitative Disclosures, Significant Inputs |
| us-gaap:OtherThanTemporaryImpairmentLossesInvestmentsAvailableforsaleSecuritiesPortionRecognizedInEarningsNetQualitativeDisclosuresSignificantInputs |
| This element represents a discussion of the significant inputs used to measure the amount of a other than temporary impairment (OTTI) of a debt security categorized as available-for-sale when only the amount related to credit loss was recognized in earnings. Examples of significant inputs include, but are not limited to, performance indicators of the underlying assets in the security (including default rates, delinquency rates, and percentage of nonperforming assets), loan to collateral value ratios, third-party guarantees, current levels of subordination, vintage, geographic concentration, and credit ratings. |
| cm:Concept |
| Text/String (xbrli:stringItemType) |
| For Period (duration) |
| (no balance type) |
| false |
| us-gaap:OtherThanTemporaryImpairmentLossesInvestmentsAvailableforsaleSecuritiesPortionRecognizedInEarningsNetQualitativeDisclosuresSignificantInputs |